Punctuation Marks With Parentheses.
Use no punctuation before the opening parenthesis except in enumerations.
Any punctuation mark can follow a closing parenthesis, but only the 3 end marks (the period, the question mark, and the exclamation point) may precede it when the parenthetical material interrupts the sentence. If a complete sentence is contained within parentheses, it is not necessary to have punctuation within the parentheses if it would noticeably interrupt the flow of the sentence. Note that with complete sentences, the initial letter of the first word is capitalized.
1) The discussion on informed consent lasted 2 hours. (A final draft has yet to be written.) The discussion failed to resolve the question.
2) The discussion on informed consent lasted 2 hours (a final draft has yet to be written) and did not resolve the question.
When the parenthetical material includes special punctuation, such as an exclamation point or a question mark, or several statements, terminal punctuation is placed inside the closing parenthesis.
1) Oscar Wilde once said (When? Where? Who knows? But I read it in a book once upon a time, hence it must be true.) that "anyone who has never written a book is very learned."